What do The Titanic, London’s Millennium Bridge, and The Leaning Tower of Pisa have in common? One answer is that as structures they all failed to “perform” as expected. The Titanic, designed with the latest technology to achieve a success rate of approximately 100% safe Atlantic transits, actually achieved a disappointing 0%. The Millennium Bridge, fine and inspiring though it was, failed to take account the consequences of perfectly natural, if little understood, human behaviour – the tendency to walk in sync on a naturally moving structure – with potentially alarming consequences. It had to be radically re-engineered before reopening in 2002.

The Leaning Tower of Pisa, which I was able to climb last month, failed in the most fundamental requirement of most buildings – staying permanently upright – though in some-ways of course this very failure was the secret of its long term success and certainly the main reason that people like me still pay good money to climb it more than 800 years after it first started leaning.

When buildings fail to deliver the intended results, we talk about a “performance gap”. While this can embrace many areas including cost, safety and comfort, we tend to talk about this particularly where energy performance is concerned. This reflects the fact that energy performance is at least ostensibly a goal of most of those involved in the design, construction and management of buildings, and that as energy prices rise and concerns over the impact of greenhouse gas emissions become more acute, the sense of urgency can only increase.

Some of the reasons for this are highlighted in a useful new book “How Much Energy Does Your Building Use?” by Liz Reason (Dō Sustainability) whose launch I attended in London last week. The book highlights examples of buildings initially hailed as energy efficient which spectacularly failed to live up to their reputation. It also shows how these failings can emerge at any stage of the building process from initial planning and design through construction, commissioning and occupation and operation, and considers how these problems and shortcomings can best be addressed and avoided.

What I want to focus on here is one central question: How do we know how our building is actually performing, let alone how it is likely to perform in future? The key here is information, which needs to be collected and then analysed, not just to show us any obvious performance issues but also point to potential problems or just unusual patterns that deserve further investigation and explanation.

This points to a central role for Building Energy Management Systems (BEMS). These are offered by a wide range of suppliers, including most of the major Building Automation providers, and present wide ranging functionality. Central to almost all of them is the collection and analysis of data, sometimes in prodigious volumes. A well implemented BEMS enables you to keep track of what your building is actually doing, irrespective of what it was intended or expected to achieve.

‘Performance gaps’ in buildings are nothing new…

Another way in which the performance gap points towards BEMS is that while the value of BEMS has been widely recognised for some time in the retrofit market, especially for the huge mass of buildings constructed in 1960 – 1990, there has sometimes been a tendency to assume that more recent buildings, being generally built to much higher standards, can, to a degree, “look after themselves”. If a building really is “zero energy” then what is there to manage, at least from an energy point of view?

However, if there are basic failings in the design itself, the way it has been implemented or commissioned, or the way the building is operated in relation to its actual usage, then the performance gap can loom up large and un-ecological as a fire-breathing dragon. Sometimes the failings can be obvious: a stiflingly uncomfortable office can jump up and hit you as much as a wildly wobbling bridge. But in other instances, energy wastage is less obvious. Real performance issues emerge only when the actual data is collected and analysed over time.

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